Electrophysiological identification of cold receptors on the antennae of the ground beetle <i>Pterostichus aethiops</i>

Abstract

Abstract. In single‐sensillum extracellular electrophysiological recordings, terminal campaniform sensilla at the tip of antennae of the ground beetle Pterostichus aethiops (Pz., 1797) show action potentials of three sensory cells, A‐, B‐ and C‐cells, distinguished by differences in their spike amplitudes. Only the A‐cell, with the largest spike amplitude, is highly sensitive to temperature fluctuations, showing remarkable changes in its firing rate induced by changes in temperature of 0.1 °C. The firing rate of A‐cells at 23 °C varies from 15–52 Hz among different beetles. Mean impulse frequency of A‐cells is found to be a function of steady temperature, the firing rate decreasing with temperature increase. A‐cells respond to a rapid temperature drop with a strong phasic‐tonic reaction; larger decreases in temperature evoke higher peak frequency values. Maximum peak frequencies, varying from 380–630 Hz in different beetles, are induced by temperature decreases of 3–10 °C, whereas temperature rise strongly inhibits impulse activity of the A‐cell. The first manifestation of rapid warming in the nerve impulse sequence is a very long interspike period, followed by diminished activity. Both the length of the long interspike period and the rate of following impulse activity are functions of temperature change; hence, A‐cells respond to temperature changes as typical cold receptors, similar to coeloconic and short hair‐like sensilla in other insects.